The present invention relates to a catalyst for oxidation of methanol to formaldehyde, to the method for preparing the catalyst, and to its use in processes for preparing formaldehyde.
Catalysts used industrially in processes for oxidation of methanol to formaldehyde (commonly termed iron molybdates, since Fe2(MoO4)3 is one of the main active components), comprise both Fe2(MoO4)3 and molybdenum trioxide (MoO3), uniformly distributed within the mass of the catalyst.
In fresh catalysts, the Fe/Mo ratio is generally higher than 1.5 and not higher than 5; however, it is subject to changes during oxidation due to losses of MoO3, which occur mainly at the inlet of the fresh reagents in the catalytic bed and in hot spot temperature regions (maximum temperature inside the reactor).
The loss of MoO3 determines decreases in the performance of the catalyst. This requires, after a more or less long period of use, the replacement of the catalyst, which is a long and expensive operation.
The loss of MoO3 causes, in addition to a reduction in the performance of the catalyst, the collapse of the catalytic bed and the consequent increase in load losses.
The need is therefore felt for a catalyst capable of providing constant performance for sufficiently long periods of time.